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Topic: Old Bits That Still Work - Muncie Transmissions (Read 5903 times)

Several folks in the "big bore" vintage racing community like to offer up the Super T-10 transmission as the best 4-speed, synchromesh gear engagement (not dog ring), "period" style gearbox for Chevy racers. I disagree, and not just because they weren't original equipment in a first generation Camaro Z/28.

I disagree because:

1) I believe a Muncie shifts better than a Super T-10. I have driven both, or rather, more Super T-10s than Muncies in race cars. I've even driven a fresh Super T-10 and a Muncie, both rebuilt and syncro-prepped by the same transmission wizard, each with fresh and similar shift linkages. In my experiences, the Muncie shifts smoother, less notchy, than a Super T-10.

2) I think the Muncie can be just as reliable. After 11 years of vintage racing a Camaro, it still has the same M21 transmission. In that time we've only done two general rebuilds, which included fresh sets of syncros.

I do think that if you're going to run a Muncie in your race car, you should do the following:

Vent the Muncie transmission from the top of the rear tailhousing, or it'll build more pressure than it needs to, and have a better chance of leaking while on the track. I hate leaks, and if sealed and prepped properly, a Muncie should not leak on the track, in the paddock, or sitting for months in the garage/shop.

Use an input bearing oil slinger, or yours may want to leak between the input splines and the nose (bearing retainer) under heavy, repeated braking that only a road race track can induce.

-Chad

PS. I did run/try a "spare" M22 transmission for one track session, but that ended with us putting back our well used M21. It wasn't the spare Muncie's fault, and it's a long story irrelevant to the above, but I bring it up because forum moderator Jon Mello was actually at that track event to see us doing this swap back to the M21. I didn't want Jon to question my credibility on the bit about 11 years of running the same transmission.

I do agree that the Muncie is a great choice in a vintage race car. You are not the only Camaro guy opting to run one but there are others who, for whatever reason, choose not to. There are many Camaros running Ford 9" rear ends and also guys who are successfully running with a 12-bolt (including yourself). Let me hear your thoughts on the 12-bolt when you have an opportunity. I really did not enjoy seeing the '69 Penske car with a 9" under it. It does not suit the history of the car.

I am a Ford guy and even I would not put a 9" in a Penske Camaro. That is just wrong. They ran them with 12 bolts back then, why not now. You can even get completely new 12 bolts these days. Don't even get me started about small block Chevys in a Ford!!

My take is that the aluminum case holds up just fine on the small cubic inch, lower torque small blocks like that which was used in the period, or in a period correct Historic Trans-Am car.

Put a big block in front of one, or even a larger small block, and indeed the case itself can become a problem. There is a great story about the Bob Jane ZL1 Camaro using a modified front case out of steel. Quoting an Australian Muscle Car magazine on the car (Issue 6, Autumn '03):

John Sawyer, Bob Jane Racing Team boss

"It originally had a Muncie (M-21) four-speed gearbox in it, then we tried a Rockcrusher (Muncie M-22) and various other things without success. I then decided that we should machine the ends off the aluminium gear housing and put ?-inch thick steel plates either end so that the housing wouldn't split. The gear strength was okay - it was actually the casing that couldn't take it. Anyway, we didn't think that modification was going to be strong enough either, so finally we made up a pair of ?-inch thick steel end-plates and actually heated up and hammered a whole new housing out of 1/8-inch steel plate. I had a very good panel man who used to work for me in those days by the name of John Brookfield. 'Brooky' did most of the fabrication work. Peter Holinger also made some special internals and a special shifter for it."

Australian Muscle Car Question

"So how did you get away with using a steel-cased gearbox when it was supposed to be cast aluminium?"

John Sawyer, Bob Jane Racing Team boss

"Well, we sandblasted it and anodized it so that it looked like aluminium! We also put the original alloy extensions and bellhousing back on it. It was bending the rules in a way, but no more than anybody else did in those days."

The above quotes were verbatim, so please don't take issue with me spelling "aluminIum" that way, or noting the steel end plates as "?-inch." And, BRUCE302, I know that American's took liberties with the spelling of this lightweight metal... But please don't ask us to say Zed-twenty-eight. And, thanks for gifting me this Australian Muscle Car magazine back in 2003.

That is a great way to get around the Muncie case issues with big torque engines (I wonder how many torques it had ?) Using steel end/spacer plates usually goes a long way to strengthening the transmission. I believe the issue is the primary shaft and main shaft trying to move away from each other. The straighter cut gears addressed the problem for production cars.

Chad, if the car came from the factory and was pronounced Zee twenty eight, then that's good enough for me. Please do me the courtesy of establishing the origin of any light metal or alloy, It could well be aluminium.

What a nightmare thinking about constructing that "home-made" steel Muncie case. As good of a fabricator as that guy "Brooky" may have been, you can't tell me that thing didn't look nasty and not like a real Muncie case.

For road racing perhaps Muncies are as good or better than a super T10 but for drag racing my experience was I broke 2 muncies per season for a couple years - first gear cluster broke each time at the light tree - switched to a Super T10 and ran it for 2 yers wtih no problems, it's still in the car today and works fine. I did have problems breaking axles after moving to the T10 - there's always a weak link it seems!